Vapor treatment of metals



being treated be dipped or rinsed in either hotV or cold water, This operation results in a more insoluble coating and is particularly advantageous when the objects are to be finished by painting or the like.

It is further recommended that after the water rinse, a final rinse be applied to the treated metal v objects which consists in a dilute solution of chromic acid. The concentration of this dual rinse may vary greatly, but for economy, suiilciently improved corrosion resistance has been obtained from a solution containing si grams per gallon of water. The chromic acid solution may be applied at a temperature ranging from. room vtemperature up to boiling and a mere wetting cf the surface is sumcient. `The metal surface is then dried before applying a finish coat.

It will be seen from the foregoing description that the present invention comprises treating metal surfaces by subjecting them to the action of the vapors of (2i-O3 or of a nitrate at a temperature of 1000 F., or below, such treatment having the eiiect of forming an oxide coating on and integral with said metal surfaces.

It is understood that the above detailed description is offered for lthe purpose of illustration and not with the intention of limiting the invention, the scope of which is to be determined by 'the appended claims.

It is within the scope of the invention to employ mixtures of the various materials used in this invention, for example, mixtures of CrGs and nitrates may be used, and when chlorine compounds are used to lower the volatilization' temperature, more than one chlorine compound may be used in the process.

What we claim is:

1. A method oi treating metal surfaces which comprises subjecting them to the action of vaporized chromic acid in combination with either ferr-ic chloride, sodium chloride or hydrochloric acid.

2. A method of treating a metal selected from the group consisting of iron. steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists of subjecting .said metal to the action of vaporized CrOa.

3. A method of treating a metal selected from the group consisting of iron, steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists of subjecting said metal to the action of vaporlzed CIO:

and a chlorine compound, at a temperature be-` low 1000 F.

4. A method of treating a metal selected from theA group consisting o iron, steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists of subjecting said metal to the action of vaporized CrOa and thereafter subjecting such treated metal to the action of a solution containing chromic acid.

5. A method of treating a metal selected from the group consisting of iron, steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists of subjectin g said metaito the action of a confined atmosphere containing vapor resulting from heating CrO; at temperatures ranging between 450 F. and 1000 F.

6. A metal article of manufacture having upon and integral with its surface a coating composed of oxides imparted throughtreatment in an atmosphere containing vapors resulting from heating CrOs and thereafter rinsing with a solution containing CrOs.

7. A metal article of manufacture having upon and integral with its surface a coating composed of oxides imparted through treatment in an atmosphere containing vapors resulting from heating CrOa and thereafter rinsing with water.

8. i method of treating metal selected from the group consistingof iron. steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists in subjecting said metal to the action of vaporized chromic acid obtained by heating asait of chromic acid in combination with a mineral acid.

9. A method of treating a. metal selected from the group consisting of iron, steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consistsin subjecting said metal to the action of vaporized chromic acid obtained by heating a salt of chromic acid in combination with phosphoric or sulphuric acid.

i0.- A method of treating a metal selected from the group consisting oi iron, steel, zinc. galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists in subjecting said metal to the action of vaporized chromic acid obtained by heating a salt of chromic acid in combination with a numeral acid at temperatures ranging between 450 and 1000 F.

1l. A method of treating a metal selected from the group consisting of iron, steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists in subjecting said metal -to the action of vaporized chromic acid obtained by heating a salt of chromic acid in combination with a mineral acid and thereafter rinsingwith a. solution containing chromic acid.

12. A method of treating a metal selected from the group consisting of iron, steel, zinc, galvanized metal, aluminum, stainless steel, rustless iron, lead, tin, terne plate, cadmium, nickel, copper and magnesium which consists of subjecting said metal to the action of vaporized CrOa and thereafter wetting the metal with a solution containing chromlc acid, and drying the metal.

13. A method of treating metal selected from the group consisting of iron and steel which consists of subjecting said metal to the action of vaporized CrOs.

14. The method of producing a rust-proofing and bonding coaton aferrous metal surface, which comprises oxidizing said surface with ongen froma gaseous source at a temperature below 1000 F. for a period sufficient to form thereon a thin continuous adherent coating of iron oxides, wetting said coating with a dilute solution of chromc acid, and drying said solution on gen from gases, which result from vaporizlng nithe surface. trete, at s. temperature below 1000 F, for s. period 15. The method of claim 14 to which is added sumcient to form thereon a thin continuous adthe step of applying a nnish coat selected from herent coating of iron oxides, wetting said coatl 5 the class o1' paints,1a.cquers and enamels. ing with a dilute solution of chromic acid, and 5 16. The method of producing a rust-proong drying said solution on the surface.

and'bonding coat on a ferrous metal surtce, y JOHN S. THOMPSON.v

which comprises oxidizing said surface ,with oxy- EDWIN W. GOODSPEED. 

